Sacnas presentation

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Synthesis, Electrochemical and Synthesis, Electrochemical and Spectroscopic Characterization of Spectroscopic Characterization of

Diruthenium Complexes with Diruthenium Complexes with Mixed Anionic Bridging LigandsMixed Anionic Bridging Ligands

Rachel Garcia

SACNAS National Conference

Friday, October 27, 2006

Department of Chemistry

University of Houston

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RuRu22 complex components complex components

RuRu22(O(O22CCHCCH33))44ClCl

Anionic bridging ligands Anionic bridging ligands surround the Rusurround the Ru22

5+5+ core which core which

also can be replaced by other also can be replaced by other bridging ligandsbridging ligands

Ru2 core in a 5+ oxidation state; are redox active

Contains an axial ligand which can be replaced by other ligands

i.e. communicating linkers

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Previous StudiesPrevious Studies

Overall Process: Substitution Reaction:Overall Process: Substitution Reaction:

RuRu22(O(O22CCHCCH33))44Cl + 4 HCl + 4 HFapFap Ru Ru22(Fap)(Fap)44Cl + 4 Cl + 4 CHCH33COCO22HH

(3,1) conformation: Ru2(Fap)4Cl

ORTEP from Bear et al. Inorg. Chem. 2001, 40, 2282-2286

2-fluoroanilino pyridinate

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ObjectiveObjective

How do the electrochemical and spectroelectrochemical properties How do the electrochemical and spectroelectrochemical properties change as you increasingly replace one acetate by Fap?change as you increasingly replace one acetate by Fap?

IntermediatesIntermediates

a) Ru2(O2CCH3)3(Fap)Cl b) Ru2(O2CCH3)2(Fap)2Cl c)Ru2(O2CCH3)(Fap)3Cl

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ApplicationApplication

Cotton and Murillo et. al. J Am. Chem. Soc. 2003, 125, 10327-10334

Precursors to supermolecular structures :Precursors to supermolecular structures :

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In MeOH, observe stepwise exchange:In MeOH, observe stepwise exchange:

SynthesisSynthesis

80° C

+

Reaction stopped at 4 hrs.

Ru2(CH3CO2)4Cl Fap ligand RuRu22(ac)(ac)22(Fap)(Fap)22ClCl

RuRu22(ac)(Fap)(ac)(Fap)33ClCl

RuRu22(ac)(ac)33(Fap)Cl(Fap)Cl

RuRu22(Fap)(Fap)44ClCl

Monitored reaction by TLC

time

3 equivalents of HFap

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PurificationPurification

FiltrationFiltration- Remove - Remove excess unreacted excess unreacted Ruthenium acetateRuthenium acetate

http://www.cdch.de/demos/laborglas/filtration.htm

SublimationSublimation- - Remove excess Remove excess unreacted bridging unreacted bridging ligandligand

ColumnColumn ChromatographyChromatography- - Separate and isolate Separate and isolate the products formedthe products formed

http://cwx.prenhall.com/horton/medialib/media_portfolio/text_images/FG03_11.JPG

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Electrochemistry of RuElectrochemistry of Ru22(Fap)(Fap)44Cl in Cl in

CHCH22ClCl22

oxidationoxidation reductionreduction

HOMO-LUMO = ∆│RedHOMO-LUMO = ∆│Red11-Ox-Ox11││

∆│ ∆│RedRed11-Ox-Ox11││

ORTEP from Bear et al. Inorg. Chem. 2001, 40, 2282-2286

01.6 -2.0Potential Potential

( V vs. SCE)( V vs. SCE)

I,II and III are all 1 electron transfers I,II and III are all 1 electron transfers

RuRu225+5+/Ru/Ru22

6+6+RuRu226+6+/Ru/Ru22

7+7+ RuRu225+5+/Ru/Ru22

4+4+

Cu

rren

tC

urr

ent

Ru2(Fap)4Cl

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Redox behaviorRedox behavior


In this study we examined the electrochemistry of the mixed ligand series where

PhCN was the solvent :


RuRu22(ac)(ac)22(Fap)(Fap)22ClCl

CompoundRu2

5+/6+Ru2

5+/4+

Ru24+/3+

0

Volts vs SCE

1.11

0.75

1.24

0.56 -0.63

-1.48

-0.57

-1.58

-0.43

-1.63Ru2

5+/6+Ru2

5+/4+

Ru24+/3+

0

Volts vs SCE

1.11

0.75

1.24

0.56 -0.63

-1.48

-0.57

-1.58

-0.43

-1.63

1.54 V

1.32 V

1.19 V

1.8 -1.7

Due to the increase of electron density around Due to the increase of electron density around the diruthenium corethe diruthenium core

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1st Half Wave Reduction Potential vs. Hammet Constant

y = -1.8x - 0.36

R2 = 0.9918

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0 0.05 0.1 0.15 0.2 0.25 0.3

Hammet Constant

Red

uct

ion

Po

ten

tial

(V

)

1st Half Wave Oxidation vs. Hammet Constant

y = -3.4667x + 1.265

R2 = 0.9918

0

0.2

0.4

0.6

0.8

1

1.2

0 0.05 0.1 0.15 0.2 0.25 0.3

Hammet Constant

Oxi

dat

ion

po

ten

tial (

V)

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UV-visible SpectroscopyUV-visible Spectroscopy

There is a red shift of the lower energy band as you increase the amount of Faps surrounding the

core

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Wavenumber of Ru25+ vs. Hammet Constant

y = -10587x + 15753

R2 = 0.9979

13000

13500

14000

14500

15000

15500

0 0.05 0.1 0.15 0.2 0.25 0.3

Hammet

Wav

enu

mb

er (

cm-1

)

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UV-visible SpectroelectrochemistryUV-visible Spectroelectrochemistry

Apply a potential to the solutionApply a potential to the solution

WE

CE

RE

N2

b

a

-0.68

-1.03

-0.80 V

0.00

0.20

0.40

0.60

0.80

1.00

1.20

300 350 400 450 500 550 600 650 700

Ab

sorb

ance

(AU

)

Wavelength (nm)A

3. Record the spectra as a function of time.

UV-visible lightthrough the thin-layer cell

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461 nm661 nm

590 nm424 nm

810 nm

437 nm690 nm

473 nm

Kadish et al. (2003). Inorg Chem 42: 8309-8319.

Ru25+ 6+Ru2

5+ 4+CompoundCompound




RuRu22(Fap)(Fap)44ClClRuRu22(ac)(ac)22(Fap)(Fap)22ClCl








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SummarySummary

The mixed ligand series, Ru2(ac)x(Fap)y where x+y = 4, were synthesized

Electrochemical studies reveal a negative shift for the 1st reduction and 1st oxidation, which can be explained by the increase of electron density around the diruthenium core as you replace the ac by Fap.

Linear relationships have been established between the number Fap ligands (the Hammet constant of fluorine) bound to the diruthenium core and the redox processes, Ru2

5+/4+ and Ru25+/6+.

With only 2 Fap’s bound to the core, spectral changes of the reduced and oxidized forms of a complex are similar to a complex with 4 Fap/s around the dimetal core.

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AcknowledgementsAcknowledgements

Dr. Kadish, my thesis advisor- for all of his help Dr. Kadish, my thesis advisor- for all of his help and support academically and financiallyand support academically and financially

Dr. “V” (Van Caemelbecke) from Houston Baptist Dr. “V” (Van Caemelbecke) from Houston Baptist University- for his great academic advice and helpUniversity- for his great academic advice and help

Dr. Chan, UH director of AGEP- financial plus Dr. Chan, UH director of AGEP- financial plus personal support and an opportunity to be here at personal support and an opportunity to be here at SACNAS SACNAS

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